I just got a kitten, about 4 months old. I don't know what kind of food he was eating before, so I started him on Iams kitten food. This is obviously the kind of abrupt diet change we are warned to avoid with cats, but there's not really anything I can do about that. He has a good appetite and seems to enjoy the Iams; however, as a result of the change in diet, he is having lots of smelly gas and loose stools. About how long should it take his digestive system to adjust to the new food? Is there anything I can give him to help the process?